Fuel systems on board vehicles of various types generally comprise devices for the ventilation of hydrocarbons contained in the tank. They may also include devices for supplying the engine with fuel. Such devices form the link between elements contained in the tank (valves, fuel pump, etc.) and elements positioned outside the tank (canister, filling pipe, etc.). The penetration through the wall of the tank must take into account the sealing requirements laid down by current environmental standards (LEV II and PZEV for example). For this purpose, the reduction in the number and size of the openings in the wall of the tank constitutes a favorable factor in reducing evaporative losses. However, this makes it more difficult to insert components into the tank and position them therein.